1. Technical Field
The present invention relates to a patterning method, a droplet discharging device, and a circuit board.
2. Related Art
An inkjet method in which a functional fluid is discharged as droplets is gaining attention as an effective technique for producing a desired pattern on a substrate (for example, refer to JP-A-2004-347695).
A conventional inkjet system includes a stage for placing a substrate, a droplet discharging head for discharging a functional fluid containing a functional material on the substrate, and a mechanism for causing relative two-dimensional movement of the substrate (stage) and the discharging head. In the inkjet system, the droplets discharged from the droplet discharge head are disposed to optional locations on the substrate surface by the relative movement of the substrate and the droplet discharging head. Droplets sequentially disposed on the substrate surface produce a pattern formed with the functional fluid. If, the droplets spread far enough to overlap with one another, the substrate surface may be completely covered without gaps.
However, when the substrate surface is repellent to the functional fluid, the attractive power with which the substrate surface pulls the droplets is weaker than the attractive pulling power working between the adjacent droplets. Therefore, the functional fluid gathers up locally on the substrate surface. Such local gathering prevents an even coverage of the functional fluid on the substrate surface. In fact, as the local gathering grows, a part of the substrate surface may become exposed due to a lack of functional fluid.
To avoid such local gathering in an inkjet system that places adjacent droplets to overlap with one another, a prior droplet needs to be sufficiently dried before a subsequent droplet is applied. As a result, a long time is required to carry out the patterning process. One suggestion to resolve this problem is to preheat the substrate so as to quickly dry the landing droplets (for instance, refer to JP-A-2004-306372 and JP-A-11-281985).
However, if the substrate temperature increases, the droplets boil violently upon landing and the pattern is not produced. Therefore, increasing the substrate temperature has imitations for increasing the drying speed, and thus there is a limit as to how short the time required for patterning can be made.